lester



C. A. LESTER.

REFLECTOR FOR AUTOMOBILE HEADLIGHTS, ETC.

APPLICATION FILED APR. 13, I920.

1,417,926, Patented -May 30, 1922.

2 SHEE TS-SHEET 1. v

C. A. LESTER.

REFLECTOR FOR AUTOMOBILE HEADLIGHTS, ETC.

APPLICATION FILED APR. 13, 1920.

1,417,926, Patented May 30, 1922.

2 SHEETS-SHEET 2- A TTOHNEYS.

UNITEB STAlES CHARLES AUSTIN LESTER.

OF WINONA, MINNESOTA.

REFLECTOR FOR AUTOMOBILE HEADLIGHTS. ETC.

Application filed April 13,

To (/77. will)? it may 1091mm Be it known that I, (lumps A. LESTER, a citizen of the Unite-d States, residing at 167 7th St. Winona, county of \Vinona and State of h linnesota, have invented certain new and useful Improvements in a Reflector for Automobile lleadlights, etc., of which the following is a specification.

My invention relates to a reflector for antomobile headlights, searchlights or similar devices. which is based upon the principle of reflection from a surface having as its elements parabolic curves of uniformly changing formulae. These elements are so combined and arranged that no reflected ray of light will rise higher than a lmrizontal line from the top of the headlight. Such a retiector is highly advantageous. in that it eliminates the glare from upwardly directed aberrant rays. which is both annoying and dangerous when such light falls upon a pedestrian or the driver of an automobile.

Two of the embodiments of my invention will be illustrated in the following drawings and description which also disclose the principle. of construction and operation thereof Figs. 1 to 6 inclusive, are diagrammatic views illustrating the mathematical principles upon which my device is based.

Fig. 7 is a perspective vertical sectional view of a practical device embodying the principles illustrated in Fig-s 1 to 6.

Fig. Sis a diagrammatic view illustrating the development of another embodiment.

Fig. 9 is an end view showing the same development.

Fig. 10 is a section of a reflector made according to the second embodiment.

FigQll illustrates the zone of illumina tion of the reflector shown in Fig. 10.

In Fig. 1, the planes A, B and C are mutually at right angles to each other, so that they intersect along the line say, which is supposed to be horizontal. and along a vertical line perpendicular to this line my.

Suppose that a paraboloid of revolution is constructed having its axis on the line my, its mouth being the circle 1, located in vertical plane A, so that the plane B passes through the axis thereof, and the plane A is at right angles to the said axis. This paraboloid is the ordinary parabolic reflector. Let the focus of the paraboloid be denoted by F the intersection of the paraboloid with Specification of Letters Patent.

Patented May 30, 1922.

1920. Serial No. 373,546.

the plane B be denoted by P and its intersection with the horizontal plane C, be de-' noted by 3. Assume that the planes B and C remain perpendicular to each other and that they are revolved about the point F as the center, the plane A remaining stationary and perpendicular to plane B until the line of intersection ma between the revolved planes B and as shown in Fig. 2, makes any required angle with the horizontal line my which may be called the parabolic axis.

Now suppose, that a parabola. which will be termed P is constructed in plane B of Fig. 2 having its focus at F, its axis ma in plane (.l as shown in Fig. 2 and the extremity of its upper limb coincident with the extremity of the upper limb of the original paraliiola described on plane B as shown in Fig. 1, and in Fig. 3.

The directrix of parabola P is denoted by D in Fig. 3 which illustrates such parabola and D will be perpendicular to mm, and the resulting parabola will have its vertex at V as shown in Fig. 8. This parabola and all the others hereinafter described stop at the vertex in the reflector itself that is, only one limb thereof is use-d in constructing my new reflector. As clearly appears from Fig. 3, the original paraboloid of revolution was constructed by revolving the pa rabola l having the directr'ix D Now suppose that a parabola is drawn.

having its focus at F. line ma for its axis and the extremity of its lower limb coincident with thatof the lower limb of P As shown in Fig. 4. this last mentioned parabola is denoted by P and its d'irectrix D is parallel to D and its vertex will be at V If now a figure is constructed in plane B as in Fig. 5 having for its upper limb, the upper limb of P and for its lower limb the lower limb of P its optical effect will be the same as the optical effect of a complete parabola having its axis on the line 72m and focus at F, but its upper and lower limbs will terminate at the ends of the upper and lower limbs of P, and these terminal points will lie in the circle 1 shown in Fig. 1.

Hence, rays of light emitted from the focus F will be reflected in a direction parallel to the line 21m.

Suppose that the plane B in Fig. 2 is rotated about the line 92m as an axis until it has made a quarter of a revolution, the line ma at the same time turning or tilting on the point F as a pivot and always remaining in 6 constructed thereon in each of its positions quarter revolution.

a vertical plane, the plane revolving and the line turning with uniform velocity so that the line ma coincides with the line my when the revolving plane B has completed its The movement of the axis 71m is'therefore always proportional to the movement of pl an B.

As the revolving plane B assumes each of a series of successive positions in the course of its revolution, suppose that a parabola is drawn therein having for its upper extremity point on the circle 1 shown in Fig. 1, its focus at the common focus F, and for its axis a line forming with the line mm, the same'fractional part of the angle mFw shown in Fig. 2 as the fractional" part of the said quarter revolution that has been completed by the revolving pl'ane B.

As the vertex of a parabola is located in its axis, all the vertices of the series of parabolas thus drawn, will be in a vertical plane such as plane B shown in Fig. 1., and the suc ,cession of points formed by the series of vertices willform a curved line extending from V to V and denoted by B as shown in Fig. The value of the angle mFr as above explained will be decreased by 1/90 thereof for every degree of revolution of the rotating plane B. Thus, if any number of degrees through which the plane B has revolved is expressed by n, then the angle formed by the linev mm at the sametin'ie with the Fixed line n mg is equal to the angle mFoc iniuus of the aiwle mFzr.

Thus,if the angle mFm shownin Figs. 2 and 3 is originally live degrees, then when the revolving plane B has revolved 4-5", the line arm will have completed of its total movement of 5, and the angle made by it in its new position with the line my will be 23f.

Similarly, when the revolving plane B has revolved l8", the'line 722% will have completed 2,: of its total movement, so that it will now make an angle of a with the line my.

When the construction has been brought to this point, the revolving planeB horizontal and is perpendicular to plane A. From this position, suppose that the re volving plane is revolved again through another quarter of a revolution about the line mm as an axis, the line ma which now c'oiu rides with the line my, siniultane'ously turu-- 'ing uniformly about the point F as a center,

always remain ing in the vertical plane, until it reaches again the pos "sally occupied by it inFig. 2. course. the s eed of the revolution of the plane B and t c movement of line VII/IL are always supposed to be uniform, therefore the same relation as before expressed will exist.

its the revolving plane occupies the succession of positions in the second quarter of I'tSIOX 'OlUUOH, suppose that a parabola is before described.

having for is lower extremity a point in the circle 1 which is shown in Fig. 1, its focus at the common focus F, and for its axis a line on the vertical plane B, the said line forming with the line my, the same fractional part of the angle mFa; the fraction of the quarter revolution which has been completed by the revolving plane.

All the vertices of the second series of parabolas form a line in the vertical plane designated by R shown in Fig. 5.

The revolving plane B now having finished half of a revolution, again occupies the position shown by plane B in Fig. 2 and one half of the reflector has been completed. The other halt may be con'ipleted in the sam way by revolution of the vertical plane in the opposite direction in a similar manner ant the complete reflector is thus formed.

The surface of this reflector has a continuously varying curvature of such a kind that it may be described as a variable parabolic surface of continuous curvature consisting of an innumerable number of parabolic curves constructed on a variable axis, every axis being in a vertical plane, and every parabola having a common focus. This surface so completed may be used as a reflector for auto headlights or the like by inserting through its vertex asdiag raiumatically shown in Fig. 6, a cylindrical socket for holding a lamp so that the axis of the cylinder coincides with the axis of the original paraboloid of revolution F shown in Fig. l, and the lamp may be placed in such position as to bring its lilament in adjustment at the coinn'ion ton-us, as shown diagramniatically in Fig. 6 and in perspective in the vertical sectional view shown in F T.

vi'uiot-her form of this reflector, which is more practicable mechanically, is developed as follows:

Construct a parabola of the desired formula on vertical plane B, Fig. 1 and let the circular mouth of the resulting paraboloid of revolutionliein plane A, as before. This may be considered as the basis or basic paral ola from which the new reflector is to be formed. Let its'focus F and its axis 003 lie in the line of intersection ofplanes B and "l shown in Fig. 1. New revolve the two planesriand (,l on F as a pivot in'such a way that planes A and G remain lllelil'oildicul'ar to each other and plane l3; remains perpendicular to plane'ir. until} line of inter-- section of planes ii and G ll'lztlIGS any required angle with their in ginal line of iiitersection, as shown by line 722/71 Fig. 2, as The parabola described on plane B will then ass'iune the position P Fig. 8. lt'willb'e noted that in Fig, 8 the focus is the same point in both positions D'f theparabola, but the upper limit of the upper limb projects beyond plane A and ill) the extremity at the lower limb does not extend to plane A. The lower limb is to be extended until it reaches plane A, and the upper limb is to be shortened an equal amount. P is now rotated about its axis, the axis at the same time being turned about l as a center, and remaining in plane B. the two movements to be simultaneous and in such a ratio that one quarter of a revolution will be accomplished at the same time that line 12m coincides with line my This ratio may be such that the rclioivi parabola will complete each fractional part of its quarter revolution at the same time that the line ma completes the same fractional part of its complete movement toward line my, or the movement of the line 71m may be in a constantly accelerated or a constantly retarded ratio to the movement ol' the paraiu ola, but in any event the two nwrcments are to terminate at the same time. When P has reached the horizontal by completing one-quarter revolution it will coincide with P in the horizontal axial plane oi the basic paraboloid of revolution. Now continue the revolution of P on its axis, and let the axis turn vertically on the focus as a pivot as before, but in a direction toward line mm. the two movements having the same ratio as before described so that when P has reached a perpendicular position the axis innv which had coiiuided with my will again assiune position ma, and l will be in the original position it occupied before starting the dcveloi iment ot the new modi lied parabolic surlace. This surl ace is one in which every element is a parabola ot' the same formula and curvature. having a constantly changing axis anu a common tocus. The other half ot the reflector is formed by correspomlingly parabolic revolving the generatrix in the opposite direction This molflilied paraboloid o'l revolution is now to be limited by plane i and its vertical central section through plane P) is shown by curve l V i, Fig. 8. This curve is a parabola with vertex at V its upper limb shorter than the lower. It now in Fig. 8 that part of the figure representing the surtacc ot plane B is considered to represent the surface of plane a section of the paraboloid in plane (l will correspoml to the original parabola a shown at l). V, it. The opening or month of the rellector will be a curved figure almost cirrular in outline lying in plane Pk. as shown in Fig. 9 Angle wal a: Fig. 8 is much exaggerated tor clearness. amounting in the diagram to about 7 degrees. whereas in actual practice would need to be about degrees. llence the ditlorente in the length of the two vertical arms of the parabola F, V G. Fig. 8,

and the distortion of the mouth of the rethe completed reflector through the vertical axial plane, showingbulb in position. The eccentricity ol the bulb in Figs. 9 and 10 is exaggerated in the same degree. The outer edge of the flange is indicated by circl ll. Fig. 9.

The principle upon which this reflector is constructed is as iollows:-

It light from an automobile headlight with its axis horizontal is thrown on a wall or screen at a given distance (as it.) away, the outline of the illuminated area is circular or approximately so. greater in diameter than the diameter oi the headlight, its center the same height trom the ground as the focus of the reflector. The highest point of the area is that point in its vertical diameter, which is illuminated. by those rays from the top of the vertical axial section ol. the reflector which deviate most widely from parallelism with the axis. In order 'tobring the top oi? the circle cl light to a point the same distance from the. ground as the top of the headlight, it is necessary to point the headlight downward until its axis forms the same angle with its original horizontal position as the angle of deviation of the rays which reach the top of the circle. For instance ii the rays deviate 5 degrees, the axis must be inclined five degrees from the hori-.

zontal. This lowers the whole pattern or circle of light so that in practice the most brilliant illumination is cast on the ground too close to the car. But the rays which emanate from the horizontal axial section illuminate the horizontal limits of the circular pattern, and with the headlight in its original position they are already horizontal, and the headlight needs no tilting to keep them from rising and ultimately blinding the approaching driver or pedestrian. That is, the rays from the vertical meridian deviate 5 degrees from parallelism with the horizontal axis, and also rise from the ground at an angle of 5 degrees, but the rays from the horizontal meridian or section of the reflector deviate from parallelism with the axis but do so transversely, and remain parallel to the ground. In the same manner, rays from any other meridian of the reflector rise from parallelism with the ground in proportion to the position of the given meridian. Thus, rays from the 45 degrce meridian will deviate 5 degrees from the axis, but will only make an angle of 2% degrees from the ground. This can readily be demonstrated by cutting in a piece of cardboard a slot l of an inch wide and as long as the diameter of the mouth of the reflector. and placing it in front of the reflector and turning it in dillercnt positions and noting the position of the band of light falling on the wall or screen. Hence if the vertical meridian of the headlight could be tilted 5 degrees the horizontal meridian left LOO &

horizontal, and the degree meridian tilted but 2*} degrees, and at the same time all other meridians tilted their proper proportional angle the highest rising ray from. every point on the reflector would be brought horizontal and a massing of horizontal rays would occur which would preserve the brilliancy of the l'iorizontal beam and at the same time no ray would rise above a line parallel to the horizontal axis. The refiector herein described equivalent in the mani'ier in which the rising i/ i: are l3i' ')tl =l'. to parallelism to an ordinary parabolic reflector gradually tilted so that rising rays from each meridian in turn becomes horizontal. l' ig. ll shows diagrammatically the modification of the illuminated area when the new reflector R is used, with the greatest intensity of illumination retained in approximately the same position as with the ordinary re iector, but-no rays rising above a line parallel with the top 01 the headlight. The lines A and B in Fig. ll denote the limits of the light from an ordinary headlight which throws the circular pattern G of light. The pattern of light cast by the new reflector is shown by a the relative Zntensity being indicated by N.

I claim 1. A parabolic reflector having its surface composed of parabolic elements whose axes make different angles with the main axis oi. the reflector, the angle made by the axis ot any given element beii'ig proportional to the angle made with the vertical meridian by the meridian in which such element is located, the axes of all said parabolic elements being located in the same plane.

2. A parabolic reflector having its surface composed-of parabolic elements whose axes make different angles with the main axis of the reflector, the said ang jgles varying in a uniform series in each quadrant ot the reflector the angle made by the axis of any given element being proportional to the an gle made with the vertical meridian. by the meridian in which s ich element is located, the axes of all sait parabolic elements being located in the same plane.

A reflector having a continuously curved reflecting surface capable of being divided into halves each half being the complement of the other, said surface being de veloped by the half revolution of a parabola about its axis, said axis being moved simultaneously with the revolution of the paraiw oia. i such a "way that during one iguarter revolution said axis is moved in a direction away from its original positiom and during the next quart r revolution toward its initial position, each arc oi the parabola during the described i'novements developing one half oi the reflector, thus by the movement of the whole parabola producing the entire surface.

4-. A reflector having a reflecting surface composed of a series of parabolic elements having a series oi axes all in the same vertical plane, which make different angles with the main axis of the reflector, the angle made by any given axis with the said main axis increasing in. each quadrant in a given ratio to the angle made by said element with a horizontal plane passed through said main axis, whereby when said main axis is held in the horizontal plane the highest-rising rays reflected from any given point on the surface of the reflector are caused to assume a substantially horizontal position.

In testimony whereof I hereunto aflix my signature.

CHARLES AUSTIN LESTER. 

